1.\" Copyright (c) 1980, 1989, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 4. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)mount.8 8.8 (Berkeley) 6/16/94 29.\" $FreeBSD$ 30.\" 31.Dd June 6, 2011 32.Dt MOUNT 8 33.Os 34.Sh NAME 35.Nm mount 36.Nd mount file systems 37.Sh SYNOPSIS 38.Nm 39.Op Fl adflpruvw 40.Op Fl F Ar fstab 41.Op Fl o Ar options 42.Op Fl t Cm ufs | Ar external_type 43.Nm 44.Op Fl dfpruvw 45.Ar special | node 46.Nm 47.Op Fl dfpruvw 48.Op Fl o Ar options 49.Op Fl t Cm ufs | Ar external_type 50.Ar special node 51.Sh DESCRIPTION 52The 53.Nm 54utility calls the 55.Xr nmount 2 56system call to prepare and graft a 57.Ar special 58device or the remote node (rhost:path) on to the file system tree at the point 59.Ar node . 60If either 61.Ar special 62or 63.Ar node 64are not provided, the appropriate information is taken from the 65.Xr fstab 5 66file. 67.Pp 68The system maintains a list of currently mounted file systems. 69If no arguments are given to 70.Nm , 71this list is printed. 72.Pp 73The options are as follows: 74.Bl -tag -width indent 75.It Fl a 76All the file systems described in 77.Xr fstab 5 78are mounted. 79Exceptions are those marked as 80.Dq Li noauto , 81those marked as 82.Dq Li late 83(unless the 84.Fl l 85option was specified), 86those excluded by the 87.Fl t 88flag (see below), or if they are already mounted (except the 89root file system which is always remounted to preserve 90traditional single user mode behavior). 91.It Fl d 92Causes everything to be done except for the actual system call. 93This option is useful in conjunction with the 94.Fl v 95flag to 96determine what the 97.Nm 98command is trying to do. 99.It Fl F Ar fstab 100Specify the 101.Pa fstab 102file to use. 103.It Fl f 104Forces the revocation of write access when trying to downgrade 105a file system mount status from read-write to read-only. 106Also 107forces the R/W mount of an unclean file system (dangerous; use with 108caution). 109.It Fl L 110When used in conjunction with the 111.Fl a 112option, mount 113.Em only 114those file systems which are marked as 115.Dq Li late . 116.It Fl l 117When used in conjunction with the 118.Fl a 119option, also mount those file systems which are marked as 120.Dq Li late . 121.It Fl n 122For compatibility with some other implementations, this flag is 123currently a no-op. 124.It Fl o 125Options are specified with a 126.Fl o 127flag followed by a comma separated string of options. 128In case of conflicting options being specified, the rightmost option 129takes effect. 130The following options are available: 131.Bl -tag -width indent 132.It Cm acls 133Enable POSIX.1e Access Control Lists, or ACLs, which can be customized via the 134.Xr setfacl 1 135and 136.Xr getfacl 1 137commands. 138This flag is mutually exclusive with 139.Cm nfsv4acls 140flag. 141.It Cm async 142All 143.Tn I/O 144to the file system should be done asynchronously. 145This is a 146.Em dangerous 147flag to set, since it does not guarantee that the file system structure 148on the disk will remain consistent. 149For this reason, the 150.Cm async 151flag should be used sparingly, and only when some data recovery 152mechanism is present. 153.It Cm current 154When used with the 155.Fl u 156flag, this is the same as specifying the options currently in effect for 157the mounted file system. 158.It Cm force 159The same as 160.Fl f ; 161forces the revocation of write access when trying to downgrade 162a file system mount status from read-write to read-only. 163Also 164forces the R/W mount of an unclean file system (dangerous; use with caution). 165.It Cm fstab 166When used with the 167.Fl u 168flag, this is the same as specifying all the options listed in the 169.Xr fstab 5 170file for the file system. 171.It Cm late 172This file system should be skipped when 173.Nm 174is run with the 175.Fl a 176flag but without the 177.Fl l 178flag. 179.It Cm mountprog Ns = Ns Aq Ar program 180Force 181.Nm 182to use the specified program to mount the file system, instead of calling 183.Xr nmount 2 184directly. 185For example: 186.Bd -literal 187mount -t foofs -o mountprog=/mydir/fooprog /dev/acd0 /mnt 188.Ed 189.It Cm multilabel 190Enable multi-label Mandatory Access Control, or MAC, on the specified file 191system. 192If the file system supports multilabel operation, individual labels will 193be maintained for each object in the file system, rather than using a 194single label for all objects. 195An alternative to the 196.Fl l 197flag in 198.Xr tunefs 8 . 199See 200.Xr mac 4 201for more information, which cause the multilabel mount flag to be set 202automatically at mount-time. 203.It Cm nfsv4acls 204Enable NFSv4 ACLs, which can be customized via the 205.Xr setfacl 1 206and 207.Xr getfacl 1 208commands. 209This flag is mutually exclusive with 210.Cm acls 211flag. 212.It Cm noasync 213Metadata I/O should be done synchronously, while data I/O should be done 214asynchronously. 215This is the default. 216.It Cm noatime 217Do not update the file access time when reading from a file. 218This option 219is useful on file systems where there are large numbers of files and 220performance is more critical than updating the file access time (which is 221rarely ever important). 222This option is currently only supported on local file systems. 223.It Cm noauto 224This file system should be skipped when 225.Nm 226is run with the 227.Fl a 228flag. 229.It Cm noclusterr 230Disable read clustering. 231.It Cm noclusterw 232Disable write clustering. 233.It Cm noexec 234Do not allow execution of any binaries on the mounted file system. 235This option is useful for a server that has file systems containing 236binaries for architectures other than its own. 237Note: This option was not designed as a security feature and no 238guarantee is made that it will prevent malicious code execution; for 239example, it is still possible to execute scripts which reside on a 240.Cm noexec 241mounted partition. 242.It Cm nosuid 243Do not allow set-user-identifier or set-group-identifier bits to take effect. 244Note: this option is worthless if a public available suid or sgid 245wrapper like 246.Xr suidperl 1 247is installed on your system. 248It is set automatically when the user does not have super-user privileges. 249.It Cm nosymfollow 250Do not follow symlinks 251on the mounted file system. 252.It Cm ro 253The same as 254.Fl r ; 255mount the file system read-only (even the super-user may not write it). 256.It Cm snapshot 257This option allows a snapshot of the specified file system to be taken. 258The 259.Fl u 260flag is required with this option. 261Note that snapshot files must be created in the file system that is being 262snapshotted. 263You may create up to 20 snapshots per file system. 264Active snapshots are recorded in the superblock, so they persist across unmount 265and remount operations and across system reboots. 266When you are done with a snapshot, it can be removed with the 267.Xr rm 1 268command. 269Snapshots may be removed in any order, however you may not get back all the 270space contained in the snapshot as another snapshot may claim some of the blocks 271that it is releasing. 272Note that the schg flag is set on snapshots to ensure that not even the root 273user can write to them. 274The unlink command makes an exception for snapshot files in that it allows them 275to be removed even though they have the schg flag set, so it is not necessary to 276clear the schg flag before removing a snapshot file. 277.Pp 278Once you have taken a snapshot, there are three interesting things that you can 279do with it: 280.Pp 281.Bl -enum -compact 282.It 283Run 284.Xr fsck 8 285on the snapshot file. 286Assuming that the file system was clean when it was mounted, you should always 287get a clean (and unchanging) result from running fsck on the snapshot. 288This is essentially what the background fsck process does. 289.Pp 290.It 291Run 292.Xr dump 8 293on the snapshot. 294You will get a dump that is consistent with the file system as of the timestamp 295of the snapshot. 296.Pp 297.It 298Mount the snapshot as a frozen image of the file system. 299To mount the snapshot 300.Pa /var/snapshot/snap1 : 301.Bd -literal 302mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4 303mount -r /dev/md4 /mnt 304.Ed 305.Pp 306You can now cruise around your frozen 307.Pa /var 308file system at 309.Pa /mnt . 310Everything will be in the same state that it was at the time the snapshot was 311taken. 312The one exception is that any earlier snapshots will appear as zero length 313files. 314When you are done with the mounted snapshot: 315.Bd -literal 316umount /mnt 317mdconfig -d -u 4 318.Ed 319.El 320.It Cm suiddir 321A directory on the mounted file system will respond to the SUID bit 322being set, by setting the owner of any new files to be the same 323as the owner of the directory. 324New directories will inherit the bit from their parents. 325Execute bits are removed from 326the file, and it will not be given to root. 327.Pp 328This feature is designed for use on fileservers serving PC users via 329ftp, SAMBA, or netatalk. 330It provides security holes for shell users and as 331such should not be used on shell machines, especially on home directories. 332This option requires the SUIDDIR 333option in the kernel to work. 334Only UFS file systems support this option. 335See 336.Xr chmod 2 337for more information. 338.It Cm sync 339All 340.Tn I/O 341to the file system should be done synchronously. 342.It Cm update 343The same as 344.Fl u ; 345indicate that the status of an already mounted file system should be changed. 346.It Cm union 347Causes the namespace at the mount point to appear as the union 348of the mounted file system root and the existing directory. 349Lookups will be done in the mounted file system first. 350If those operations fail due to a non-existent file the underlying 351directory is then accessed. 352All creates are done in the mounted file system. 353.El 354.Pp 355Any additional options specific to a file system type that is not 356one of the internally known types (see the 357.Fl t 358option) may be passed as a comma separated list; these options are 359distinguished by a leading 360.Dq \&- 361(dash). 362For example, the 363.Nm 364command: 365.Bd -literal -offset indent 366mount -t cd9660 -o -e /dev/cd0 /cdrom 367.Ed 368.Pp 369causes 370.Nm 371to execute the equivalent of: 372.Bd -literal -offset indent 373/sbin/mount_cd9660 -e /dev/cd0 /cdrom 374.Ed 375.Pp 376Options that take a value are specified using the -option=value syntax: 377.Bd -literal -offset indent 378mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt 379.Ed 380.Pp 381is equivalent to 382.Bd -literal -offset indent 383/sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt 384.Ed 385.Pp 386Additional options specific to file system types 387which are not internally known 388(see the description of the 389.Fl t 390option below) 391may be described in the manual pages for the associated 392.Pa /sbin/mount_ Ns Sy XXX 393utilities. 394.It Fl p 395Print mount information in 396.Xr fstab 5 397format. 398Implies also the 399.Fl v 400option. 401.It Fl r 402The file system is to be mounted read-only. 403Mount the file system read-only (even the super-user may not write it). 404The same as the 405.Cm ro 406argument to the 407.Fl o 408option. 409.It Fl t Cm ufs | Ar external_type 410The argument following the 411.Fl t 412is used to indicate the file system type. 413The type 414.Cm ufs 415is the default. 416The 417.Fl t 418option can be used 419to indicate that the actions should only be taken on 420file systems of the specified type. 421More than one type may be specified in a comma separated list. 422The list of file system types can be prefixed with 423.Dq Li no 424to specify the file system types for which action should 425.Em not 426be taken. 427For example, the 428.Nm 429command: 430.Bd -literal -offset indent 431mount -a -t nonfs,nullfs 432.Ed 433.Pp 434mounts all file systems except those of type 435.Tn NFS 436and 437.Tn NULLFS . 438.Pp 439The default behavior of 440.Nm 441is to pass the 442.Fl t 443option directly to the 444.Xr nmount 2 445system call in the 446.Li fstype 447option. 448.Pp 449However, for the following file system types: 450.Cm cd9660 , 451.Cm mfs , 452.Cm msdosfs , 453.Cm nfs , 454.Cm nullfs , 455.Cm oldnfs , 456.Cm smbfs , 457.Cm udf , 458and 459.Cm unionfs . 460.Nm 461will not call 462.Xr nmount 2 463directly and will instead attempt to execute a program in 464.Pa /sbin/mount_ Ns Sy XXX 465where 466.Sy XXX 467is replaced by the file system type name. 468For example, nfs file systems are mounted by the program 469.Pa /sbin/mount_nfs . 470.Pp 471Most file systems will be dynamically loaded by the kernel 472if not already present, and if the kernel module is available. 473.It Fl u 474The 475.Fl u 476flag indicates that the status of an already mounted file 477system should be changed. 478Any of the options discussed above (the 479.Fl o 480option) 481may be changed; 482also a file system can be changed from read-only to read-write 483or vice versa. 484An attempt to change from read-write to read-only will fail if any 485files on the file system are currently open for writing unless the 486.Fl f 487flag is also specified. 488The set of options is determined by applying the options specified 489in the argument to 490.Fl o 491and finally applying the 492.Fl r 493or 494.Fl w 495option. 496.It Fl v 497Verbose mode. 498If the 499.Fl v 500is used alone, show all file systems, including those that were mounted with the 501.Dv MNT_IGNORE 502flag and show additional information about each file system (including fsid 503when run by root). 504.It Fl w 505The file system object is to be read and write. 506.El 507.Sh ENVIRONMENT 508.Bl -tag -width ".Ev PATH_FSTAB" 509.It Ev PATH_FSTAB 510If the environment variable 511.Ev PATH_FSTAB 512is set, all operations are performed against the specified file. 513.Ev PATH_FSTAB 514will not be honored if the process environment or memory address space is 515considered 516.Dq tainted . 517(See 518.Xr issetugid 2 519for more information.) 520.El 521.Sh FILES 522.Bl -tag -width /etc/fstab -compact 523.It Pa /etc/fstab 524file system table 525.El 526.Sh DIAGNOSTICS 527Various, most of them are self-explanatory. 528.Pp 529.Dl XXXXX file system is not available 530.Pp 531The kernel does not support the respective file system type. 532Note that 533support for a particular file system might be provided either on a static 534(kernel compile-time), or dynamic basis (loaded as a kernel module by 535.Xr kldload 8 ) . 536.Sh SEE ALSO 537.Xr getfacl 1 , 538.Xr setfacl 1 , 539.Xr nmount 2 , 540.Xr acl 3 , 541.Xr mac 4 , 542.Xr devfs 5 , 543.Xr ext2fs 5 , 544.Xr fstab 5 , 545.Xr procfs 5 , 546.Xr kldload 8 , 547.Xr mount_cd9660 8 , 548.Xr mount_msdosfs 8 , 549.Xr mount_nfs 8 , 550.Xr mount_nullfs 8 , 551.Xr mount_smbfs 8 , 552.Xr mount_udf 8 , 553.Xr mount_unionfs 8 , 554.Xr umount 8 , 555.Xr zfs 8 , 556.Xr zpool 8 557.Sh HISTORY 558A 559.Nm 560utility appeared in 561.At v1 . 562.Sh CAVEATS 563After a successful 564.Nm , 565the permissions on the original mount point determine if 566.Pa ..\& 567is accessible from the mounted file system. 568The minimum permissions for 569the mount point for traversal across the mount point in both 570directions to be possible for all users is 0111 (execute for all). 571.Pp 572Use of the 573.Nm 574is preferred over the use of the file system specific 575.Pa mount_ Ns Sy XXX 576commands. 577In particular, 578.Xr mountd 8 579gets a 580.Dv SIGHUP 581signal (that causes an update of the export list) 582only when the file system is mounted via 583.Nm . 584.Sh BUGS 585It is possible for a corrupted file system to cause a crash. 586